Design, manufacturing and installation of the JT-60SA vacuum vessel gravity support

摘要

In the operation of JT-60SA tokamak device, such loads as electromagnetic (horizontal and vertical loads of 2.5 MN and 7.5 MN, respectively) and seismic are imposed on the VV, and thermal expansion takes place during the baking of Vacuum Vessel (VV). The nine Vacuum Vessel Gravity Supports (GSs) have to support the loads and total dead weight of 400 tons including in-vessel components and compensate thermal deformation. Assembling to realize precise positioning of each GS to the VV is indispensable in the limited space between toroidal field coils. To meet the design requirements described above, a GS is equipped with an assembly of flexible plates (FPs) in its lower part and a stem in its upper part with external thread that is screwed upward on the internal thread of VV stub for installation. Electric discharge machining is applied to form FPs without welding. Narrow gap TIG and electron beam welding are also adopted to suppress welding distortion. By the FEM analysis-based design and successful product manufacturing, we have established a design concept and manufacturing technology of GS that has both stiffness and flexibility. The installation mock-up test of GS has also successfully finished.